A number of cephalosporin antibiotics having a substituent directly substituted on the carbon at the 3-position of the cephem ring system are known. For example, the 3-hydroxy and 3-methoxy substituted 3-cephem compounds described by Chauvette in U.S. Pat. Nos. 3,917,587 and 3,917,588; the 3-halo-3-cephem compounds described by Chauvette in U.S. Pat. Nos. 3,925,372 and 3,962,227; the 3-sulfonyloxy-3-cephem and 3-sec.-amino-3-cephem compounds described by Spitzer in U.S. Pat. Nos. 3,985,737 and 4,013,651, respectively; and the 3-heterocyclic thio substituted 3-cephems described in U.S. Pat. No. 3,992,377. Many 3-substituted methyl-3-cephem compounds are known in the cephalosporin art. Among the 3-substituted methyl-3-cephem compounds which have been described are the 3-azidomethyl substituted cephalosporins, U.S. Pat. Nos. 3,274,186, 3,278,531, 3,360,515 and 3,634,418. The 3-azidomethyl-3-cephem compounds have been converted to 3-aminomethyl-3-cephem antibiotics and Heymes et al. have prepared cephalosporin .gamma.-lactams with the 3-aminomethyl-3 -cephem compounds. 7-Azido cephalosporins are disclosed as useful intermediates by Christensen et al. in U.S. Pat. No. 4,297,488.